Derivative Instruments (Detail Effect Of Derivative Assets And Liabilities In Statement Of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Derivatives In Cash Flow Hedging Relationship [Member] | Commodity Derivatives [Member] | Revenues [Member]
Change in value recognized in OCI on derivatives (effective portion)	$ 0	$ (16,996)
Amount of gain (loss) reclassified from AOCI into income (effective portion)	0	(3,429)
Amount of gain (loss) recognized in income on ineffective portion	0	88
Amount of gain (loss) recognized in income on pre-hedge designation fair value	0	1,627
Derivatives Not Designated In A Hedging Relationships [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	2,965	2,316
Derivatives Not Designated In A Hedging Relationships [Member] | Commodity Derivatives [Member] | Revenues [Member]
Amount of gain (loss) from designation amortized from AOCI into income	(3,665)	0
Derivative Instruments, Gain (Loss) Recognized in Income, Net	2,481	0
Derivatives Not Designated In A Hedging Relationships [Member] | Interest Rate [Member] | Interest Expense, Net [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(12)	(259)
Derivatives Not Designated In A Hedging Relationships [Member] | Embedded Derivatives [Member] | Other Income and Deductions, Net [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 496	$ 2,575